The present invention relates to a spinner for use during semiconductor device fabrication and, more particularly, to an improved structure of a cup of the spinner for protecting the surface of a semiconductor that has been coated with a liquid from particles spun off of the semiconductor surface from returning to the surface.
During the fabrication of most semiconductor devices, it is necessary to coat the surface of the semiconductor wafer with different fluids, e.g. photoresist or developer. The method of coating the semiconductor wafer typically includes placing the semiconductor wafer on a chuck, fastening the semiconductor wafer to the chuck, spinning the chuck/semiconductor combination at a high speed and then spraying the fluid onto the surface of the semiconductor. The coating is spread out into a relatively even film and the excess is spun off by centrifugal force. This process is commonly known as "spinning on photoresist" or the like in the art.
In the conventional technology, a cup that includes a deflecting surface inclined downward is disposed around the spinner. The cup does not contact the semiconductor or its coating. This deflecting surface is located at the same height as the semiconductor so that most of the excess fluid from the coating, as well as any impurities in the coating, is spun off the semiconductor surface in the form of particles which then impact the cup at the deflecting surface. This surface deflects the particles downward, away from the semiconductor surface and toward a drain. The bottom of the cup typically contains holes for evacuation of any gaseous or particulate matter in the interior of the cup introduced during processing.
The problem in the conventional spinner described above is that, at the spin speeds necessary for processing, while most of the particles are spun off the semiconductor radially and deflected downward, a significant number will be lifted aerodynamically. These particles may reflect back on to the surface of the semiconductor instead of being deflected toward the drain. The particles that return to the surface of the semiconductor surface create unevenness in the thickness of the film, filaments in the film or resist balls, and are thus typically a source of defects brought about during the photolithographic process. Consequently, the present art requires a structure to eliminate the reflected particles and accordingly, the source of these defects. Because the production of semiconductor devices from a semiconductor wafer depends critically on the parameters used in the necessary photolithographic processes, any irregularity in the coating creates defects. These defects in turn result in a decrease in the yield of devices created from these semiconductor wafers.